REI Hobitat 4
Hobitat 4 (courtesy, REI)

What are tent coatings and deniers?

I’m looking for a new family tent and confused about fabric ratings. One store’s website says something about 1,000mm coatings, but I don't see any references to that on other sites. I did see one that said "70 denier." What's that and how do I compare? Robin Highland, Indiana

REI Hobitat 4

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Coatings and deniers are different things, but equally confusing. We’ll start with coatings. All tents have polyurethane coating on the floor and waterproof fly, and it’s the coating that keeps you dry, not the fabric itself. A coating of, say, 1,000mm doesn’t mean the coating is that thick—that would make it nearly 40 inches thick. Instead, it’s a measure of how much hydrostatic pressure the coating can take before it leaks. That test is accomplished by securing a selected piece of fabric to the end of a long tube, to which water is added. The 1,000mm designation means that 1,000mm of water can be added before the coating leaks.

REI Hobitat 4

REI Hobitat 4 Hobitat 4

Obviously, a higher number is better, as a thin coating is less resistant to abrasion and therefore more apt to fail. For a tent floor, I’d say about 1,000mm pressure resistance is the minimum for wet conditions. The fly can get away with a lower rating because you’re not kneeling on it and potentially squeezing water through the fabric. High-end backpacking tents will have floor coatings rated to as much as 3,500mm.

Denier (pronounced den-YAY) is a unit of measurement that applies to a yarn’s thickness. Packs often have fabric with a denier of 500 or more—pretty heavy stuff, for more durability (but also with big gaps between fibers, which is why it’s so difficult to waterproof a pack). Clothing uses much finer yarn, so the denier there is often around 70 or so. In tents you’ll find a mix, depending on where the fabric is used, with a denier of 75 and 150 most commonly found.

You don’t say what kind of tent you’re looking for. If car camping, then a good choice for a family of four is REI’s new Hobitat 4 ($259; or Hobitat 6 ($329). These are exceptionally sturdy tents for their size, with a rugged 300-denier floor and a coating rated to 1,500mm. I also like the Eureka! Equinox ($349;, which sleeps six. Its floor is rated to 1,200mm.

I almost always recommend that tent users place something under the tent to protect the floor from abrasion. Most tent manufacturers will happily sell you a “footprint” for $40 or more. But you can buy some light polyethylene sheeting at your local hardware store and cut yourself a piece. Make it slightly smaller than the size of the floor, so water dripping off the tent doesn’t catch on the footprint and collect under the tent.

The votes are in: Check out the winners of Outside‘s 2006 Gear of the Year awards, including the year’s hottest tent.

From Outside Magazine, April/May 2021
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Lead Photo: courtesy, REI

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